Detection system and method of diffractive optical element

Abstract

The present application provides a detection system and method for a diffractive optical element, the detection system comprising: a light source, a beam splitter, a fixing part and a detection part, the light source is used to emit linearly polarized light to the beam splitter; the beam splitter is used to split the received linearly polarized light into two beams of linearly polarized light with equal amplitude and at a preset angle; the fixing part is used to fix the diffractive optical element to be tested; the detection part is used to receive a diffraction beam to detect the diffractive optical element to be tested, wherein the diffraction beam is a beam formed by the diffraction optical element to be tested diffracting the two beams of linearly polarized light. In this way, there is no need to rotate or move the DOE in the process of detecting the DOE in two directions, which can improve the detection efficiency of the DOE on the one hand, and on the other hand, there is no need to place the DOE twice, which can minimize the possibility of damage to the DOE, thereby improving the safety of the detection system of the diffractive optical element during the detection of the DOE.

Description

Technical Field

[0001] The present application relates to the field of 3D imaging technology. Specifically, it relates to a detection system and method for diffractive optical elements. Background Art

[0002] A diffractive optical element (DOE) is a rapidly developing new type of optical element, which is widely used in the laser projection module of a 3D (3-Dimension) depth camera. The performance of the DOE directly affects the quality of the projected pattern and further affects the depth imaging effect of the depth camera.

[0003] The diffraction behavior of the DOE can be divided into quasi-static region diffraction (grating constant d < λ / 2), resonance region diffraction (λ / 2 < d < 10λ), and scalar diffraction region (d > 10λ). The differences among the three diffractions mainly result from the different interactions between light waves and the DOE. Correspondingly, the research theories of the DOE diffraction characteristics are divided into two major categories: scalar diffraction theory and vector diffraction theory. Generally, the grating structure period d of the DOE and the designed light wavelength λ are of the same order of magnitude (λ < d < 10λ), and the two are in the resonance region. Moreover, the complex grating structure of the DOE has the characteristic of anisotropy, and this grating structure will produce a transmission loss phenomenon related to the light polarization direction.

[0004] In the existing detection systems for the DOE, the light sources used are all linearly polarized lights. When testing the performance of the DOE, it is usually necessary to test twice, that is, to detect the DOE in two directions of 0 degree and rotated 90 degrees respectively. This detection method not only has low detection efficiency, but also is extremely easy to damage the product during the testing process. Summary of the Invention

[0005] The purpose of the embodiments of the present application is to provide a detection system and method for diffractive optical elements to detect the diffractive optical elements efficiently and safely.

[0006] To achieve the above purpose, the embodiments of the present application are implemented as follows:

[0007] In a first aspect, the embodiments of the present application provide a detection system for diffractive optical elements, including: a light source, a beam splitting part, a fixing part, and a detection part. The light source is used to emit linearly polarized light to the beam splitting part; the beam splitting part is used to split the received linearly polarized light into two linearly polarized lights with equal amplitudes and a preset angle; the fixing part is used to fix the diffractive optical element to be measured; the detection part is used to receive the diffracted light beam to detect the diffractive optical element to be measured, where the diffracted light beam is the light beam formed by the diffractive optical element to be measured diffracting the two linearly polarized lights.

[0008] In the embodiment of the present application, the detection system of the diffractive optical element includes a beam splitter, which can split the linear polarized light emitted by the received light source into two beams of linear polarized light with equal amplitude and at a preset angle, so that when the detection system of the diffractive optical element performs a performance test on the DOE, the DOE can be detected according to the diffraction beam formed by the diffractive optical element to be tested (i.e., DOE) diffracting the two beams of linear polarized light. In this way, there is no need to rotate or move the DOE in the process of detecting the DOE in two directions. On the other hand, there is no need to place the DOE twice, which can minimize the possibility of damage to the DOE, thereby improving the safety of the detection system of the diffractive optical element during the detection of the DOE.

[0009] In combination with the first aspect, in a first possible implementation manner of the first aspect, the preset angle is 90°.

[0010] In this implementation, since the grating structure of the DOE has anisotropic characteristics, it means that this grating structure of the DOE will produce transmission loss related to the polarization direction of the light. That is, the DOE performance is closely related to the angle α between the polarization direction of the incident light and the grating groove direction of the DOE. Generally, when the polarization direction of the incident light is parallel to the grating groove direction, that is, the angle α = 0 degrees, the DOE performance is the best and the conversion efficiency is the highest. When the polarization direction of the incident light is perpendicular to the grating groove direction, that is, the angle α = 90 degrees, the DOE performance is the worst and the conversion efficiency is the lowest. Therefore, the preset angle for the DOE performance detection is set to 90°, and the beam splitter can split the received linearly polarized light into two beams of linearly polarized light with equal amplitudes and 90°, so as to ensure the accuracy and effectiveness of the detection as much as possible.

[0011] In combination with the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the beam splitter is a quarter wave plate.

[0012] In this implementation, a quarter wave plate is used as a beam splitter, so that the received linearly polarized light can be simply and efficiently split into two linearly polarized lights with equal amplitudes and an angle of 90°.

[0013] In combination with the first possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the beam splitter is a polarization direction rotator.

[0014] In this implementation, a polarization direction rotator is used as a beam splitting section, and the angle of the beam splitting can be flexibly set (the preset angle can also be set to 90°).

[0015] In combination with the first aspect, in a fourth possible implementation of the first aspect, the detection unit includes a projection screen and a receiving device, the projection screen is used to receive the diffraction light beam and form an image; the receiving device is used to obtain the diffraction image on the projection screen and process the diffraction image to determine the detection result of the diffraction optical element to be tested.

[0016] In this implementation, the detection unit includes a projection screen and a receiving device, and the receiving device can obtain the diffraction image on the projection screen and process it to determine the detection result of the diffractive optical element to be tested. In this way, the diffractive optical element to be tested can be accurately detected.

[0017] In combination with the first aspect, in a fifth possible implementation manner of the first aspect, the light source is a collimated single-point laser.

[0018] In this implementation, a single-point laser is used as a light source, which can save the need for collimating a traditional light source, and is beneficial for optimizing the structure of a detection system of a diffractive optical element.

[0019] In combination with the first aspect, in a sixth possible implementation of the first aspect, the detection system of the diffractive optical element also includes a control unit, which is respectively connected to the light source and the detection unit, and is used to control the light source to emit linearly polarized light, and to control the detection unit to collect the diffraction light beam to detect the diffractive optical element to be tested.

[0020] In combination with the first aspect, or in combination with any possible implementation of the first to sixth aspects, in a seventh possible implementation of the first aspect, the light source, the beam splitter, the fixing part and the detection part are located on the same axis.

[0021] In this implementation, the light source, the beam splitting part, the fixing part and the detection part are located on the same axis, which is conducive to ensuring the accuracy of the detection.

[0022] In a second aspect, an embodiment of the present application provides a method for detecting a diffractive optical element, which is applied to a detection system for a diffractive optical element according to the first aspect or any one of the possible implementations of the first aspect, the method comprising: emitting linearly polarized light to the beam splitting portion by the light source; splitting the received linearly polarized light into two beams of linearly polarized light with equal amplitude and at a preset angle by the beam splitting portion, and projecting the two beams of linearly polarized light to the diffractive optical element to be measured fixed by the fixing portion; diffracting the two beams of linearly polarized light at a preset angle by the diffractive optical element to be measured, and projecting a diffraction light beam generated by the diffraction to the detection portion; receiving the diffraction light beam by the detection portion to detect the diffractive optical element to be measured.

[0023] In combination with the second aspect, in a first possible implementation of the second aspect, when the detection unit includes a projection screen and a receiving device, the diffraction light beam is received by the detection unit to detect the diffraction optical element to be measured, including: receiving the diffraction light beam and imaging it through the projection screen; acquiring the diffraction image on the projection screen through the receiving device, and processing the diffraction image to determine the detection result of the diffraction optical element to be measured.

[0024] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 A schematic diagram of the structure of a laser projection module provided in an embodiment of the present application.

[0027] Figure 2 The diffraction spot patterns at 0° and 90° are provided in the embodiments of the present application.

[0028] Figure 3 A structural schematic diagram of a detection system for a diffractive optical element is provided for an embodiment of the present application.

[0029] Figure 4 A flowchart of a method for detecting a diffractive optical element is provided for an embodiment of the present application.

[0030] Icons: 100 - laser projection module; 101 - VCSEL light source; 102 - collimator; 103 - diffractive optical element; 200 - detection system of diffractive optical element; 210 - light source; 220 - beam splitter; 230 - fixing part; 240 - detection part; 241 - projection screen; 242 - receiving device. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0032] Before describing the detection system of the diffractive optical element provided in the embodiment of the present application, its background is first introduced here to facilitate the understanding of the present solution.

[0033] Diffractive optical elements (i.e., DOE) are a new type of optical element with rapid development and can be applied to the laser projection module of 3D depth cameras. Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a laser projection module 100 provided by an embodiment of the present application.

[0034] In this embodiment, the laser projection module 100 may include a VCSEL light source 101, a collimating mirror 102, and a diffractive optical element 103.

[0035] Among them, the VCSEL light source 101 may be a two-dimensional VCSEL light source 101 arranged in a two-dimensional pattern composed of multiple sub-light sources. For the convenience of description here, Figure 1 only three sub-light sources are exemplarily given on a one-dimensional level, but it should not be regarded as a limitation to the present application. Compared with traditional laser light sources, the VCSEL light source 101 has the advantages of small volume and small divergence angle, but at the same time has the characteristic that the polarization directions of the emitted laser light are inconsistent, that is, the polarization directions of the emitted light of each light-emitting point are not the same. Therefore, a collimating mirror 102 can be used for collimation.

[0036] Exemplarily, the collimating mirror 102 can receive the light beam (with inconsistent polarization directions) emitted by the VCSEL light source 101 and collimate the light beam with a certain divergence angle (i.e., the light beam emitted by the VCSEL light source 101).

[0037] Exemplarily, the diffractive optical element 103 can be used to receive the light beam collimated by the collimating mirror 102 and project a diffracted light beam into the target space through the way of light diffraction. This diffracted light beam is formed by replicating the VCSEL light source 101. For example, if the VCSEL light source 101 has 100 sub-light sources and the replication number of the diffractive optical element 103 is 100, then 10,000 speckle points will be formed in the space.

[0038] The diffraction behavior of the diffractive optical element 103 can be divided into quasi-static region diffraction (grating constant d < λ / 2), resonance region diffraction (λ / 2 < d < 10λ), and scalar diffraction region (d > 10λ), where λ is the wavelength of light. The main differences among the three diffraction behaviors lie in the different interactions between the light wave and the diffractive optical element 103. Correspondingly, the research theories of the diffraction characteristics of the diffractive optical element 103 are also divided into two major categories: scalar diffraction theory and vector diffraction theory.

[0039] In the field of structured light or optical TOF (Time Of Flight), the size of the grating period d of the diffractive optical element 103 is usually in the same order of magnitude as the wavelength λ (λ = 940nm). The grating structure of the diffractive optical element 103 has anisotropy, which is very similar to the anisotropy of crystals, which means that the grating structure of the diffractive optical element 103 will produce transmission loss related to the polarization direction of light. That is, the performance of the diffractive optical element 103 is closely related to the angle α between the polarization direction of the incident light and the grating groove direction of the diffractive optical element 103. In general, when the polarization direction of the incident light is parallel to the grating groove direction (i.e., α = 0°), the performance of the diffractive optical element 103 is the best and the conversion efficiency is the highest; when the polarization direction of the incident light is perpendicular to the grating groove direction (i.e., α = 90°), the performance of the diffractive optical element 103 is the worst and the conversion efficiency is the lowest.

[0040] In order to eliminate the error caused by the polarization direction of the incident light to the performance test of the diffractive optical element 103, the diffractive optical element 103 may be tested in the direction of α=0° to obtain the following: Figure 2 Then, the diffraction optical element 103 can be rotated 90° counterclockwise, at which α=90°, and the diffraction optical element 103 is tested again to obtain the following: Figure 2 The diffraction spot pattern of part B in FIG. Then, the light intensity corresponding to each spot can be averaged to obtain the detection result. For example, Figure 2 The black dots in part A and part B represent light spots of the same diffraction order. By taking the average of the light intensities corresponding to the points in the two diffraction patterns (part A and part B), we can get the light intensity corresponding to the point.

[0041] However, the existing detection method has the problem of low detection efficiency because it needs to rotate the diffractive optical element 103 and detect twice. On the other hand, in the process of rotating the diffractive optical element 103, the microstructure of the diffractive optical element 103 is easily damaged, thereby causing additional loss of the diffractive optical element 103.

[0042] Based on the above questions, please refer to Figure 3 The embodiment of the present application provides a detection system 200 for a diffractive optical element to detect the diffractive optical element 103 safely and efficiently.

[0043] In this embodiment, the detection system 200 of the diffractive optical element may include: a light source 210, a beam splitter 220, a fixing part 230 and a detection part 240. The light source 210 is used to emit linearly polarized light to the beam splitter 220. The beam splitter 220 can split the received linearly polarized light into two beams of linearly polarized light with equal amplitudes and at a preset angle. The fixing part 230 is used to fix the diffractive optical element to be tested. The detection part 240 can receive the diffraction beam to detect the diffractive optical element to be tested, wherein the diffraction beam is a beam formed by the diffraction optical element to be tested diffracting the two beams of linearly polarized light.

[0044] In order to ensure the accuracy of detection, the light source 210, the beam splitter 220, the fixing part 230 and the detection part 240 may be located on the same axis. Of course, this is not limited to this. For example, the fixing part 230 may not be located on the same axis as the light source 210, the beam splitter 220 and the detection part 240. It is only necessary that when the diffractive optical element to be detected is detected, the diffractive optical element to be detected disposed on the fixing part 230 is located on the same axis as the light source 210, the beam splitter 220 and the detection part 240.

[0045] For example, in order to ensure the accuracy of detection, the linearly polarized light emitted by the light source 210 needs to be collimated. Therefore, the light source 210 can be a collimated single-point laser. Using a single-point laser as a light source can save the part of collimating the traditional light source, which is conducive to optimizing the structure of the detection system of the diffractive optical element.

[0046] Of course, the light source 210 may also adopt a traditional light source (the polarization directions of the emitted light beams are inconsistent), such as a VCSEL light source, and in order to obtain collimated linearly polarized light, the light source 210 may also include a collimator for collimating the linearly polarized light emitted by the VCSEL light source. Therefore, there is no limitation here, and the type of light source 210 can be selected according to actual needs. In addition, the VCSEL light source and the collimator are divided into the description of the light source 210 here, just for the convenience of explanation. In some other feasible ways, the VCSEL light source and the collimator can also be used as independent parts of the detection system 200 of the diffractive optical element, which is not limited here.

[0047] In order to achieve safe and efficient detection of the diffractive optical element, illustratively, the beam splitter 220 can be used to split the received linear polarized light into two beams of linear polarized light with equal amplitude and at a preset angle. After the beam splitter 220 splits the received linear polarized light into two beams of linear polarized light with equal amplitude and at a preset angle, when the diffractive optical element to be detected is detected, the diffractive optical element to be detected can be detected in different directions during one detection process, without moving or rotating the diffractive optical element to be detected during the detection process.

[0048] On the one hand, this can improve the detection efficiency of the diffractive optical element to be measured. On the other hand, since there is no need to rotate the diffractive optical element to be measured, damage to the microstructure of the diffractive optical element to be measured during the rotation process can be effectively avoided, thereby minimizing the possibility of causing damage to the diffractive optical element to be measured, thereby improving the safety of the diffractive optical element detection system 200 during the detection process of the diffractive optical element to be measured.

[0049] In order to ensure the accuracy of the detection of the diffractive optical element, the preset angle can be 90° (the principle can be found in the previous text). It should be noted that the 90° here can be within a certain error range, such as an error range of 0.1°, but it should not be regarded as a limitation, and the error range can be set according to actual needs.

[0050] It should be noted that the preset angle of 90° is selected here based on the currently more effective detection method. When it is determined that other angles can also achieve good detection effects, the preset angle can also be set to the corresponding angle. Therefore, this should not be regarded as a limitation on this application.

[0051] In order to achieve the splitting unit 220 to split the received linear polarized light into two beams of linear polarized light with equal amplitude and 90°, the beam splitting unit 220 can use a 1 / 4 wave plate. Of course, when the preset angle is other angles, a glass slide that realizes the angle can be selected as the beam splitting unit 220, which is not limited here. In this way, the received linear polarized light can be simply and efficiently split into two beams of linear polarized light with equal amplitude and 90°. In addition, the use of a 1 / 4 wave plate makes the structure and the setting method of the detection system 200 of the diffractive optical element simple and low in cost.

[0052] Specifically, when using a quarter wave plate for beam splitting, the linearly polarized light emitted by the light source 210 can first be perpendicularly incident on the quarter wave plate, and the polarization direction of the light can be adjusted to form a 45° angle with the optical axis plane of the quarter wave plate. At this time, after the linearly polarized light enters the quarter wave plate, two linearly polarized lights with equal amplitudes and perpendicular directions will be generated, and the amplitudes of the two light beams are I×cos45° and I×sin45°, respectively, where I is the amplitude of the incident light. The two linearly polarized lights with equal amplitudes and perpendicular directions can be incident on the diffractive optical element to be measured, so that the diffractive optical element to be measured forms a diffraction beam that is projected outward, so that the detection unit 240 receives the diffraction beam, and the detection of the diffractive optical element to be measured is realized.

[0053] In addition, light sources with different wavelengths can correspond to 1 / 4 wave plates of different designs. Here, the role of the 1 / 4 wave plate is to decompose the incident light beam into two linearly polarized lights with equal amplitudes and perpendicular polarization directions, that is, the polarization directions are respectively along the 0° direction and the 90° direction. After the two linearly polarized lights are diffracted, the light intensity of the diffracted light beam (or diffraction image) detected by the detection unit 240 is equivalent to the average light intensity of the light beam when the diffractive optical element to be tested is tested at 0° and 90° respectively without the 1 / 4 wave plate.

[0054] Exemplarily, the beam splitter 220 may also use a polarization direction rotator to split the received linear polarized light into two beams of linear polarized light with equal amplitude and at a preset angle. For example, a polarization direction rotator is used to split the received linear polarized light into two beams of linear polarized light with equal amplitude and at a 90° angle.

[0055] By using a polarization direction rotator as the beam splitter 220, the angle of the beam splitting can be flexibly set. Generally, the polarization direction rotator can continuously rotate the polarization direction of the linearly polarized incident light by at least 180° without generating mechanical movement, and the adjustable range is very flexible. In the entire rotation range, the polarization direction rotator can ensure that the minimum extinction ratio is greater than 1000:1. There are many types of polarization direction rotators (such as liquid crystal polarization direction rotators). The polarization direction of the incident light beam is controlled by the polarization direction rotator, such as scanning within 0° to 180° with a step size of 1°. The detection unit 240 can be used to detect the diffracted light beam (or diffraction image) to record the change in its light intensity. The recorded data can not only obtain the average value of the light intensity of the light beams at 0° and 90°, but also take the maximum light intensity value and the minimum light intensity value to calculate the polarization dependent loss (PDL), which is a parameter used to describe the sensitivity of the performance of the diffractive optical element to be tested to the polarization state of the incident light beam.

[0056] In this embodiment, the fixing portion 230 is used to place the diffractive optical element to be measured, and may be a clamping member, an inserting member, etc., so as to fix the diffractive optical element to be measured, which is not limited here.

[0057] In this embodiment, the detection unit 240 may include a projection screen 241 and a receiving device 242, wherein the projection screen 241 may receive a diffraction beam and form an image; and the receiving device 242 may be used to obtain a diffraction image on the projection screen 241, and process the diffraction image to determine the detection result of the diffraction optical element to be measured, thereby achieving accurate detection of the diffraction optical element to be measured. The receiving device 242 may include an image sensor and an image processing device, so that the diffraction image on the projection screen 241 is obtained by the image sensor, and the image processing device can detect the diffraction optical element to be measured according to the diffraction image.

[0058] In this embodiment, in order to realize efficient operation of the detection system 200 of the diffractive optical element, the detection system 200 of the diffractive optical element may further include a control unit. The control unit may be connected to the light source 210 and the detection unit 240 respectively, and is used to control the light source 210 to emit linearly polarized light, and to control the detection unit 240 to collect the diffraction light beam to detect the diffractive optical element to be detected.

[0059] Based on the same inventive concept, an embodiment of the present application also provides a detection method for a detection system applied to a diffractive optical element.

[0060] See also Figure 4 , Figure 4 A flow chart of a method for detecting a diffractive optical element provided in an embodiment of the present application. In this embodiment, the method for detecting a diffractive optical element may include: step S10, step S20, step S30 and step S40.

[0061] In order to achieve efficient and safe detection of the diffractive optical element to be tested, a detection system for the diffractive optical element may be used to detect the diffractive optical element to be tested.

[0062] For example, the diffractive optical element to be measured can be placed at a corresponding position on the fixing part, and the detection system of the diffractive optical element can be calibrated. For example, the parameters of each component in the detection system of the diffractive optical element and the distance between the components can be set to produce clear and sharp imaging.

[0063] After the detection system of the diffractive optical element is calibrated, the detection system may execute step S10.

[0064] Step S10: emitting linearly polarized light to the beam splitting section through the light source.

[0065] Exemplarily, the detection system can control the light source to emit linearly polarized light. For example, when the light source uses a VCSEL light source and a collimator to obtain collimated linearly polarized light, the light source can be controlled to emit preset linearly polarized light, which is then collimated by the collimator and then emitted to the beam splitter.

[0066] After emitting the linearly polarized light to the beam splitting section, the detection system may perform step S20.

[0067] Step S20: splitting the received linearly polarized light into two beams of linearly polarized light with equal amplitude and at a preset angle by the beam splitting part, and projecting the two beams of linearly polarized light onto the diffractive optical element to be measured fixed by the fixing part.

[0068] Exemplarily, the detection system can split the received collimated linearly polarized light into two beams of linearly polarized light with equal amplitude and a preset angle (eg, 90°) through a beam splitter, and project the two beams of linearly polarized light onto the diffractive optical element to be measured fixed by a fixing part.

[0069] After projecting the two beams of linearly polarized light onto the diffractive optical element to be measured fixed by the fixing part, the detection system may execute step S30.

[0070] Step S30: diffracting two beams of linearly polarized light at a preset angle by the diffractive optical element to be tested, and projecting the diffracted light beams generated by the diffraction to the detection unit.

[0071] Exemplarily, the detection system can diffract two beams of linearly polarized light at a preset angle (eg, 90°) through the diffractive optical element to be detected, and project the diffracted light beams generated by the diffraction to the detection unit.

[0072] After projecting the diffracted light beam generated by diffraction to the detection part, the detection system may execute step S40.

[0073] Step S40: receiving the diffraction light beam through the detection unit to detect the diffractive optical element to be tested.

[0074] Exemplarily, the detection system may receive the diffraction light beam through the detection unit to detect the diffraction optical element to be detected.

[0075] Specifically, the detection system can receive the diffraction beam and form an image through the projection screen of the detection unit, and obtain the diffraction image on the projection screen through the receiving device, and process the diffraction image to determine the detection result of the diffraction optical element to be tested. For example, the diffraction image is obtained from the image sensor through the image processing device of the receiving device in the detection unit (the image sensor detects the diffraction image on the projection screen), and then the diffraction image is processed and calculated to detect the performance of the diffraction optical element to be tested.

[0076] It should be noted that, through the detection method of the diffractive optical element provided in the embodiment of the present application, it is possible to detect various optical properties of the diffractive optical element to be tested.

[0077] Exemplarily, the detection of the number of spots of the diffractive optical element to be tested can be realized: for the DOE (diffractive optical element) used in the structured light depth camera, its main function is to act as a light beam splitter, forming a light spot array image composed of multiple light spots. The quality of the DOE design will directly affect the number of spots of the beam splitting and the diffraction effect of the suppression order. The full-field diffraction image can be collected first, and then each light spot of the full-field diffraction image is extracted and the number of spots is counted, and the number of spots is output as the result. If the number of spots does not match the preset number of spots (for example, the number of spots does not meet the requirements), it is determined that the DOE has not met its relevant indicators.

[0078] For example, the diffraction efficiency of the diffractive optical element to be tested can be detected: the diffraction efficiency refers to the ratio of the total intensity of the diffracted light beam emitted by the DOE to the intensity of the incident light beam incident on the DOE, which reflects the diffraction effect of the DOE. The higher the diffraction efficiency, the lower the power consumption requirement of the light source for generating a diffraction light beam pattern of the same intensity.

[0079] Since the diffraction effect of DOE is usually difficult to quantitatively measure directly by the total intensity of the diffracted beam, in this solution, an indirect method can be used to calculate the diffraction efficiency, for example, by extracting the pixel value of the acquired full-field diffraction image. Specifically, according to a preset pixel value threshold, the pixel values ​​of the spot images at each level of the full-field diffraction image with a size above the threshold can be extracted, and then the ratio of the sum of the grayscale values ​​of the spot images at each level of the full-field diffraction image to the total grayscale value of the full-field image can be used as the diffraction efficiency to achieve indirect detection of the diffraction efficiency.

[0080] Exemplarily, the zero-order size of the diffractive optical element to be tested can be detected: the zero-order size can represent the ratio of the zero-order spot energy to the adjacent first-order spot energy. Here, the zero-order uniformity (i.e., the zero-order size) can also be detected by indirect detection. For example, according to the acquired full-field diffraction image, in combination with a preset pixel threshold, the pixel values ​​corresponding to the zero-order spot and each adjacent first-order spot that exceed the preset pixel threshold are extracted, and the ratio of the sum of the grayscale values ​​of the extracted zero-order spot to the grayscale average value of the adjacent first-order spot can be used as the zero-order size.

[0081] Exemplarily, the global uniformity of the diffractive optical element to be tested can also be detected: the global uniformity is used to measure the uniformity of the light intensity of each diffraction order in the full-field diffraction image. Here, the global uniformity can also be detected by indirect detection. Specifically, according to the preset grayscale threshold, the pixel values ​​of the grayscale values ​​of the pixels of each level of the spot in the full-field diffraction image that are greater than the preset grayscale threshold are extracted, where the maximum value (I max ) and minimum value (I min) divided by the sum of the maximum and minimum values ​​is the global uniformity:

[0082]

[0083] Wherein, uniformity represents the global uniformity of the diffractive optical element to be measured.

[0084] Exemplarily, the polarization-dependent loss of the diffractive optical element to be tested can also be detected. Polarization-dependent loss is a transmission loss phenomenon of an optical device related to the polarization state of light, and is the maximum transmission difference of an optical device or system under all polarization states. Its definition formula is as follows:

[0085]

[0086] Among them, T max represents the maximum light intensity in all polarization states, T min Represents the minimum light intensity under all polarization states.

[0087] Of course, through the detection system and detection method of the diffractive optical element provided in the embodiment of the present application, some other optical properties of the diffractive optical element to be tested can also be detected, which will not be described one by one here, but these should not be regarded as limitations of the present application.

[0088] In summary, the embodiments of the present application provide a detection system and method for a diffractive optical element. The detection system of the diffractive optical element includes a beam splitter, which can split the linearly polarized light emitted by the received light source into two beams of linearly polarized light with equal amplitudes and at a preset angle. In this way, when the detection system of the diffractive optical element performs a performance test on the DOE, the DOE can be detected according to the diffraction light beams formed by the diffraction optical element to be tested (i.e., the DOE) diffracting the two beams of linearly polarized light. In this way, there is no need to rotate or move the DOE in order to detect the DOE in two directions. On the one hand, the detection efficiency of the DOE can be improved. On the other hand, there is no need to place the DOE twice, which can minimize the possibility of damage to the DOE, thereby improving the safety of the detection system of the diffractive optical element during the detection of the DOE.

[0089] In the embodiments provided in the present application, it should be understood that the disclosed systems and methods can be implemented in other ways. The system embodiments described above are merely schematic. For example, the division of the components is merely an exemplary division, and there may be other divisions in actual implementation. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some communication interface, device or unit, which may be electrical, mechanical or other forms.

[0090] In addition, the components described separately may or may not be physically separated, and the displayed components may or may not be physical units. Some or all of the components may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0091] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0092] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A detection system for a diffractive optical element, characterized in that: include: Light source, beam splitter, fixing unit and detection unit, The light source is used to emit linearly polarized light to the beam splitting portion; The beam splitting unit is used to split the received linearly polarized light into two beams of linearly polarized light with equal amplitudes and at a preset angle; The fixing part is used to fix the diffractive optical element to be measured; The detection unit is used to receive a diffraction light beam to detect the diffraction optical element to be tested, wherein the diffraction light beam is a light beam formed by the diffraction optical element to be tested diffracting the two beams of linearly polarized light; Among them, the detection of the diffractive optical element to be measured includes: detecting at least one of the number of spots of the diffractive optical element to be measured, detecting the diffraction efficiency of the diffractive optical element to be measured, detecting the zero-order size of the diffractive optical element to be measured, detecting the global uniformity of the diffractive optical element to be measured, and detecting the polarization-related loss of the diffractive optical element to be measured.

2. The detection system of the diffractive optical element according to claim 1, characterized in that: The preset angle is 90°.

3. The detection system of the diffractive optical element according to claim 2, characterized in that: The beam splitter is a quarter wave plate.

4. The detection system of the diffractive optical element according to claim 2, characterized in that: The beam splitting section is a polarization direction rotator.

5. The detection system of a diffractive optical element according to claim 1, characterized in that: The detection unit includes a projection screen and a receiving device. The projection screen is used to receive the diffracted light beam and form an image; The receiving device is used to obtain the diffraction image on the projection screen and process the diffraction image to determine the detection result of the diffraction optical element to be tested.

6. The detection system of a diffractive optical element according to claim 1, characterized in that: The light source is a collimated single-point laser.

7. The detection system of a diffractive optical element according to claim 1, characterized in that: The detection system of the diffractive optical element further includes a control unit, The control unit is connected to the light source and the detection unit respectively, and is used to control the light source to emit linearly polarized light, and to control the detection unit to collect the diffraction light beam to detect the diffraction optical element to be tested.

8. The detection system of a diffractive optical element according to any one of claims 1 to 7, characterized in that: The light source, the beam splitting portion, the fixing portion and the detecting portion are located on the same axis.

9. A method for detecting a diffractive optical element, characterized in that: A detection system for a diffractive optical element according to any one of claims 1 to 8, wherein the method comprises: emitting linearly polarized light to the beam splitting portion through the light source; Splitting the received linearly polarized light into two beams of linearly polarized light with equal amplitudes and at a preset angle by the beam splitting portion, and projecting the two beams of linearly polarized light onto the diffractive optical element to be measured fixed by the fixing portion; diffracting two beams of linearly polarized light at a preset angle by the diffractive optical element to be measured, and projecting the diffracted light beams generated by the diffraction to the detection unit; Receiving the diffracted light beam through the detection unit to detect the diffractive optical element to be tested; Among them, the detection of the diffractive optical element to be measured includes: detecting at least one of the number of spots of the diffractive optical element to be measured, detecting the diffraction efficiency of the diffractive optical element to be measured, detecting the zero-order size of the diffractive optical element to be measured, detecting the global uniformity of the diffractive optical element to be measured, and detecting the polarization-related loss of the diffractive optical element to be measured.

10. The method for detecting a diffractive optical element according to claim 9, characterized in that: When the detection unit includes a projection screen and a receiving device, receiving the diffracted light beam by the detection unit to detect the diffractive optical element to be detected includes: Receiving the diffracted light beam and forming an image through the projection screen; The diffraction image on the projection screen is acquired by the receiving device, and the diffraction image is processed to determine the detection result of the diffraction optical element to be tested.

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